A combination cooler includes a condenser and an oil cooler integrated into one heat exchanger assembly. The condenser is part of the air conditioning system and performs heat exchange from a refrigerant to the outside air. The oil cooler is part of another circuit that performs heat exchange from oil, such as automatic transmission fluid, to the outside air. The purpose of the combination cooler is to reduce weight, packaging space and cost.
Due to different fluid physical properties, the ideal tube design is different for each fluid. Considering separate components, the condenser uses smaller tubes with smaller hydraulic diameter relative to the oil cooler tubes. To keep the pressure drop low, the oil cooler uses larger tubes with a larger hydraulic diameter due to higher viscosity compared with refrigerant. Typically a disadvantage of larger tubes is lower heat transfer performance per constant internal fluid flow, as airside surface area is reduced per fixed packaging space.
In one combination cooler design, the condenser region and the oil cooler region use two distinct core configurations. Such a configuration allows specialized tube design for each region to achieve maximum performance. Possible disadvantages may include complex core design and limited oil cooler flexibility and performance.
In another combination cooler design, the condenser and oil cooler are designed to use a common core structure. The advantages are simpler core assembly utilizing common tube and fins. A possible disadvantage however is that an optimal tube diameter for refrigerant through the condenser region is different than an optimal tube diameter for oil through the oil cooler.